Field of the Invention
The embodiments disclosed herein relate to a power conversion apparatus and a method for analyzing for an abnormality in a power conversion apparatus.
Discussion of the Background
Some power conversion apparatuses are equipped with inverters to generate alternating-current (AC) power, and many of such power conversion apparatuses are used to drive motors. As this kind of power conversion apparatus, Japanese Patent No. 5370724 discloses a motor control apparatus that includes an inverter to generate AC power from direct-current (DC) power.
The motor control apparatus disclosed in Japanese Patent No. 5370724 includes a gate drive circuit, a PWM (pulse width modulation) generation circuit, and two tri-state buffers. The gate drive circuit drives the inverter. The PWM generation circuit generates PWM signals to be supplied to the gate drive circuit. The two tri-state buffers are coupled in series between the gate drive circuit and the PWM generation circuit. The gates of the two tri-state buffers are opened and closed in conjunction with handling of two external shutdown switches respectively corresponding to the two tri-state buffers. In the motor control apparatus, the two external shutdown switches respectively close the gates of the two tri-state buffers to cut off the supply of the PWM signals to the gate drive circuit, in order to stop the inverter and stop the motor. This eliminates the need for an electromagnetic contactor conventionally disposed between the motor and the inverter. This, in turn, saves the space of the motor control apparatus, and reduces the cost of the system as a whole. In addition, duplicated safety shutdown circuitry of the shutdown switches and the tri-state buffers improves safety.
The motor control apparatus generates a logical product of signals indicating an abnormality of the tri-state buffer. This enables an external upper level apparatus to determine an abnormality of the safety shutdown circuit itself, which further improves safety.